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R205 Rear Underspoiler Kit

The R205 rear underspoiler rectifies the airflow exiting from underneath the car in order to generate rear downforce and enhance brake cooling and exhaust flow extraction. Used on the limited edition R205 model and fitted to STI's 2010 24hr Nurburgring competition car. Dark gray painted finish. Note that fitment with aftermarket exhaust systems is not guaranteed.

Usually ships within 2 to 4 weeks

Manufacturer: STI

  • Subaru Impreza STI (5-Door) MY08-14

How does this product work? This item works partly as a diffuser to allow the high velocity airflow beneath the car to decelerate and expand and then directs that airflow upward to join the air stream coming off the top of the car. The result is to make the underbody more efficient, increasing downforce and reducing drag.

Can you briefly explain aerodynamic lift, downforce, and drag as it affects a car? Aerodynamic lift occurs when air pressures acting on the bottom side of the vehicle (or component) are higher than that acting on the top side resulting in a net upward force. Downforce is negative lift. The lift forces add or subtract from the forces affecting the tire contact patches and therefore will alter available traction. The distribution of lift will affect the handling balance if the effect on the front and rear wheels is not equal. Drag is a measure of the air resistance acting on the vehicle. Lift, downforce, and drag forces increase exponentially with speed.

Does this really provide a noticeable performance advantage? The benefits will only be noticeable at very high speeds and therefore in a street application it should be considered purely as a style enhancement. However, it has a legitimate place on a track car. It should be used in combination with the STI front lip spoiler for maximum effect.